Parameterization of mixing in stratified open channel flow
نویسندگان
چکیده
The dynamics and parameterization of mixing in temporally evolving turbulent open-channel flow is investigated through direct numerical simulations as the transitions from an initially neutral state to stable stratification. We observe three distinctly different regimes separated by transitional values Froude number $Fr$ : a weakly stratified regime for $Fr >1$ ; intermediate $0.3< Fr<1$ saturated $Fr<0.3$ . coefficient $\varGamma =B/\epsilon _K$ , (where $B$ buoyancy flux $\epsilon dissipation rate kinetic energy), well predicted schemes Maffioli et al. ( J. Fluid Mech. vol. 794, 2016) Garanaik & Venayagamoorthy 867, 2019, pp. 323–333) across all instantaneous measurements ratio $L_E/L_O$ where $L_E$ $L_O$ are Ellison Ozmidov length scales, respectively. Richardson $R_f = B/(B+\epsilon _K)$ shows linear dependence on gradient $Ri_g$ up value $Ri_g =0.25$ past which it saturates again constant independent or By examining balance inertial, shear forces, we derive physically based scaling relationships demonstrate that \sim Fr^{-2}$ Fr^{-1}$ moderately becomes regime. Our results suggest $L_E/L_O manifests due influence mean shear. differences between non-sheared flows within this discussed.
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ژورنال
عنوان ژورنال: Journal of Fluid Mechanics
سال: 2022
ISSN: ['0022-1120', '1469-7645']
DOI: https://doi.org/10.1017/jfm.2021.1159